The present invention relates to magnetic belts for magnetic printers and the like and, more particularly, to a novel magnetic belt having a conductive coating.
Magnetic printing systems, such as is described in U.S. Pat. 3,946,404, issued Mar. 23, 1976 and assigned to the assignee of the present invention, are known which utilize a magnetic recording belt on which a latent magnetic image is formed by a magnetic recording head, for subsequent selective transfer of ink patterns to a permanent media. As described in the aforementioned patent, a magnetic recording tape is comprised of a plastic resin backing layer upon which is fabricated a ferromagnetic recording layer; the belt is caused to travel past a magnetic recording head array to magnetize the ferromagnetic material of the recording layer in a direction in accordance with the magnetic field established by the head responsive to externally derived electronic signals. Among the properties required of such a magnetic belt, on which latent magnetic images are formed by a magnetic recording head, are the following: the belt must be thin enough to have the necessary degree of flexibility; the oxide coating of the ferromagnetic recording layer must not only have adequate magnetic performance but must also be of a thickness to permit the recording field to properly orient magnetized recording areas therein and then permit the recorded image to attract ink (toner) for subsequent transfer to a permanent medium (e.g. paper); the electrical conductivity of the oxide coating must be high enough to prevent accumulation of electric charge which would attract toner to areas which should be blank, thereby causing undesirable "background" along with the desired recorded image; and the belt must have a relatively high abrasion resistance to resist wear as one side of the belt travels over a supporting surface of the magnetic recording head. Thus, a sufficiently high value of remanence B.sub.R must be achieved in conjunction with a relatively high conductivity, typically expressed as a surface resistivity of less than 10.sup.9 ohms per square. This combination of properties is not easily achieved in known magnetic tapes as the relatively high value of B.sub.R requires a high volume fraction of magnetic oxide, in the ferromagnetic recording layer, which indicates that less volume of the layer is available for any additives utilized to increase conductivity of the recording layer.
A magnetic recording belt having a ferromagnetic recording layer having a relatively high value of B.sub.R, in excess of 1400 gauss, but having a surface resistivity less than 10.sup.9 ohms per square, is desirable for use in magnetic printing applications.